A substrate processing apparatus configured to perform various processes such as cleaning, coating of resist, development after exposure, and so forth on a semiconductor wafer (hereinafter, simply referred to as “wafer”) as a substrate includes a substrate transfer device which is configured to transfer the wafer to be processed from a carrier accommodating the wafer to a processing module in which the various processes are performed.
In such a substrate processing apparatus, there is set a maximum value of the number of wafers capable of being processed per a unit time (in the following description, the number of wafers capable of being processed for about an hour (wph) will be referred to as “throughput”), which is determined based on the number of processing modules provided in the apparatus, a processing time, and the like. An operating speed of the wafer transfer device is set to be high enough not to generate standby time caused by the operation of the wafer transfer device itself when the processing modules are operated under the conditions for achieving the maximum throughput.
In the actual substrate processing apparatus, however, the time required to complete a process in a processing module may vary depending on the content of the process or set processing conditions. The processing module may not always be operated under the conditions of achieving the maximum throughput. If the operating speed of the wafer transfer device is set to be the high value of achieving the maximum throughput even under the processing conditions where the maximum throughput can be achieved, the wafer transfer device may be overloaded, so that wear-out of components of the wafer transfer device may be advanced.
To solve this problem, Patent Document 1 describes a technique of decreasing a transfer speed of a substrate transfer device when the standby time is generated because a process in a processing chamber is not completed, in case of transferring a substrate between the processing chamber (processing module) configured to perform the process and a load lock chamber (front end module) configured to be switched between a normal pressure atmosphere and a vacuum atmosphere in a processing apparatus of performing an etching process on a glass substrate for use in a FPD (Flat Panel Display).    Patent Document 1: Japanese Patent Laid-open Publication No. 2010-283285 (paragraphs [0046] to [0050] and FIG. 7)
In Patent Document 1, in relation to the etching process time in the processing chamber, when the standby time is generated in replacing the substrate within the processing chamber, the operating speed of the substrate transfer device is reduced to make the timing when the etching of the current substrate is completed and the timing when a next substrate arrives at the processing chamber coincident. As in this case, however, if the operating speed of the substrate transfer device is easily changed in consideration of the timing when the etching process is completed, the operating speed of the substrate transfer device may be changed to an operating speed at which an operation check is not made. The operating speed at which the operation check is not made may result in a failure of a substrate transfer. Thus, there has been a demand for a technique capable of altering the operating speed of the substrate transfer device while guaranteeing reliability of the substrate transfer.